Interface Function

interface Function {
    async: boolean;
    body: FunctionBody | null;
    declare?: boolean;
    end: number;
    expression: false;
    generator: boolean;
    id: BindingIdentifier | null;
    params: ParamPattern[];
    parent?: Node;
    range?: [number, number];
    returnType?: TSTypeAnnotation | null;
    start: number;
    type: FunctionType;
    typeParameters?: TSTypeParameterDeclaration | null;
}